Electrical detonator



Oct. 29, 1968 R. PRZYBYLIK ET AL 3,407,732

ELECTRICAL DETONATOR Filed March 8, 1967 BAP/06E 6 8 0 U W U WW H m6 l m56 HP P% we MR 5 um M1 MM Z AM 1 1 i Q A A V United States PatentELECTRICAL DETONATOR Ria Prz'yliylik, Tarnowskie Gory'nl; Piastowsks';16, Poland, and Wiktor Zalachowski, Krupski Mlyn ul. Mickiewicza 3,Poland t 1 Filed Mar. 8,1967, Ser.- No. 621,536 Claims priority,application Poland, Mar. 8, 1966, e 113,388

5 Claims. (Cl. 10228) ABSTRACT OF THE prsctofsuizs Wire bridg detonatorincluding a plurailty of wires of different diameter, to give differentdelay times.

Known electric'delayed action millisecond detonators give desired delaysat firing, due to the location in the detoi'iatorshell of a'dela'yelement, which is placed between the, ignition-headand the ignition.primary said de-. lay element being the'characteristicelement ofdetonators of this type. Such delay element consists for-a tube filledwith a retarding mass, which burns at a determined velocity.

The delay time from the moment of switching on of current to the momentof the detonation is usually adjusted by an adequate length of the tubewith the retarding mass. A delayed action detonator can be manufacturedas a series by adjustment of lengths of the respective tubes.

In the known millisecond detonators, the time intervals betweendetonators of a series are generally about 25 or or more milliseconds.The smallest technically obtainable limit of interfire time betweenparticular detonators of this type is about 20 milliseconds.

The above generally described process for manufacturing detonators isvery difficult from the technological point of view due to the necessityof precise maintenance of technological parameters in the production ofthe delay mass and the delay elements. Even the smallest divergences intechnological process may result in a great undesired scatter of delaytimes in the detonators.

In another more simple technical solution, the detonator is constructedwithout separate delay elements and the retarding mass is pressed intothe shell directly onto its ignition primer. However, the delayed-actiondetonators of this type are not safe in methane and coal dustenvironment and so they are not fit for use in coal mining.

There are also known delayed-action detonators wherein the desireddelays are obtained by means of faster or slower burning ignitionmasses, located in the ignition heads of detonators. For each detonatorin the series the ignition head includes another kind of ignition mass.The manufacturing process of such detonators is also complicated, due tothe difficulty of preparing successful ignition masses for detonatorswith longer delays. On account of this, this latter process is used formaking detonator series consisting of only four detonators which is notsufiicient for the requirements of present mining works.

An object of the invention is the provision of a cheap andcon-structionally simple delayed-action detonator.

The construction of delayed-action electrical detonators of millisecondsorder is based, according to the invention,

on a new concept in reference to the theory of the ignition ofelectrical bridge detonators.

The detonators according to the invention are not provided with specialdelay elements and their ignition heads contain the same. ignition massfor each delay time. The desired delays are obtained by the applicationof ignition heads, provided with resistance wires of different thick-.

ness for different delay times.

It is commonly known that in electrical bridge detonators, a currentimpulse causes an incandescence of the resistance wire which bridges theelectrodes of the head and simultaneously ignites the head ignitionmass.This impulse is called the ignition impulse and its magnitude to a highdegree is dependent on the diameter of the resistance wire involved.

By maintaining other parameters constant, the dependence of ignitionimpulse on the thickness of wire is given by the formula:

(l) I=K.d where I=impulse of ignition, K=a constant depending on variousother parameters d=diameter of the resistance wire.

It is also known that the current impulse is:

where i=current intensity (in this case of the current which fires thedetonator) t=time of current passage from the moment of switching on ofthe detonator to the moment of ignition of the head (ignition time).

From the Formulas 1 and 2 it follows thati.e., the ignition time isproportional to fourth power of resistance wire diameter and inverselyproportional to the second power of current intensity. With constantcurrent intensity, the thicker the resistance wire the longer will bethe ignition time of head and the reaction time of the whole detonator.

On this formula is based the new concept of the delayedaction electricdetonator series of the invention. Such detonator series according tothe invention may include an optional number of detonators practically(e.g., from a few to twenty) with diiferent delays, in which the firingdelays of particular detonators are predetermined on the basis of theabove formula.

The detonators according to the invention are to be connected inparallel. However, parallel connection required careful wiring ofshooting lines on account of the limited possibility of control ofelectric circuit resistance.

As a source of electric current for firing such a detonator series,direct current or industrial current is used. Long-acting electrodynamicigniters of adequate power are also suitable.

The delay time between the separate numbers, as well as the delay rangeof the whole detonator series can be optionally adjusted within largelimits by changing the intensity of current, omitting some of the delaytimes, or by adding additional ones to the series.

The detonator of the invention can incorporate a wide variety ofdesigns. One such design which can be improved according to theinvention appears in Sewerage and Sewage Treatment by Harold E. Babbitt,Sixth Edition, John Wiley & Sons, Inc., p. 183 (chapter entitledConstruction of Sewers).

As shown in the drawing, the detonaator may include a metal shell inwhich are loaded a sulphur filling layer 12.

Patented Qct. 29, 1958 3 a sulphur plug 14, an ignition charge 16, apriming charge 18 and a base charge 20. Bridge 22 is located in ignitioncharge 16. The bridge 22 consists of a plurality of wires of differentdiameter, wires 24 and 26 being illustrated by way of non-limitativeexample. These wires are connected in parallel with DC. source 28 viaswitch 30. A selector switch 32 is provided to select the wire to beeffective.

It is to be understood that the drawing is illustrative only as variousother structures can be employed to embody the improvements of theinvention. Thus, for example, the invention also envisages a pluralityof individual detonators each provided with a wire of differentdiameter, the detonators being used separately or being connected inparallel.

The advantage of the detonators according to the invention is theirsimple construction. Due to this fact, the manufacture of thesedetonators is easy and much cheaper than for those which containconventional delay elements. Moreover, the possibility of obtaining veryshort intershoot time delays of millisecond order between the detonatorsis now possible according to the invention.

Examples DetonatorNo 1 2 3 4 5 6 7 8 Diameter otwireln microns 10(1 Thesaid detonators were connected in parallel. When fired by using varioussources of current, they have shown delay times as follows:

at-407,732.. J .J i

What is claimed is:

1. Detonation apparatus comprising ignition means and, in said means, aplurality of electrically conductive bridge. wires of differentcross-sections to elfect dilferent delays.

2. Apparatus as claimed in claim 1, wherein said'means is a singleignition charge and said wires are embedded in said charge, comprisingmeans to apply electrical current to a selected one of said wires.

3. Apparatus as claimed in claim 1, wherein said means includes aplurality of charges and said wires are respectively embedded in saidcharges.

BEN AMI ABORCHELT, Primary Examiner. V. R. PENDEGRASS, AssistantExaminer.

